Method and apparatus for scaling the dynamic range of a receiver for continuously optimizing performance versus power consumption

ABSTRACT

Methods and apparatus are disclosed for operating a RF receiver. The method executes, during operation of the RF receiver, by periodically determining existing RF receiver operational conditions; determining RF receiver performance requirements based at least in part on the determined existing RF receiver operational conditions; and by allocating power consumption between RF receiver functional blocks in accordance with the determined RF receiver performance requirements and in accordance with a behavior model of at least one of the RF receiver as a whole and individual functional blocks of the RF receiver. The method may also monitor the resulting RF receiver signal quality to determine if allocation of power consumption has resulted in an optimum allocation of the power consumption.

CLAIM OF PRIORITY FROM A COPENDING PROVISIONAL PATENT APPLICATION

[0001] This patent application claims priority under 35 U.S.C. 119(e)from copending provisional patent application No. 60/344,699, filed onDec. 28, 2001.

TECHNICAL FIELD

[0002] These teachings relate generally to radio frequency (RF)receivers and, more specifically, relate to methods and apparatus foroptimizing the performance of receivers such as those found in cellulartelephones and other types of mobile communication devices andterminals.

BACKGROUND

[0003] The following abbreviations are herewith defined.

[0004] ADC analog-to-digital converter

[0005] AM amplitude modulation

[0006] ASIC application specific integrated circuit

[0007] BB baseband

[0008] BER bit error rate

[0009] BLER block error rate

[0010] CDMA code division multiple access

[0011] CPU central processing unit

[0012] CRC cyclic redundancy check

[0013] DPCH dedicated physical channel

[0014] DS-CDMA direct sequence CDMA

[0015] DSP digital signal processing

[0016] Ec/Io code power-to-in-band interference ratio

[0017] EVM error vector magnitude

[0018] FDD frequency division duplexing

[0019] FPGA field programmable gate array

[0020] IC integrated circuit

[0021] ICP input compression point

[0022] IF intermediate frequency

[0023] IIP2 second-order input intercept point

[0024] IIP3 third-order input intercept point

[0025] IMD2 second-order intermodulation product

[0026] IMD3 third-order intermodulation product

[0027] ISI intersymbol interference

[0028] LNA low noise amplifier

[0029] LO local oscillator

[0030] MDS minimum detectable signal

[0031] MS mobile station

[0032] NF noise figure

[0033] QoS quality of service

[0034] RX receiver

[0035] RF radio frequency

[0036] RSS received signal strength

[0037] SIR signal-to-interference ratio

[0038] SNR signal-to-noise ratio

[0039] TX transmitter

[0040] VCO voltage controlled oscillator

[0041] WCDMA wide bandwidth CDMA

[0042] 3G third-generation (cellular communications system)

[0043] The dynamic range requirements of a radio receiver are normallydefined by the system specifications assuming worst-case operationalconditions. However, the worst case conditions are rarely encounteredduring the typical operation of the receiver. In general, the strengthof the received signal and any interfering signals depends on thedistance from the transmitter and on the particular radio channel,including fading and other effects.

[0044] Substantially all radio receivers in mobile terminals, such ascellular telephones and other types of mobile receivers use some type ofautomatic gain control mechanism in the receiver for compensating fordynamically changing reception conditions. The total gain of thereceiver is adjusted to the desired level for the received signaldetector or analog-to-digital converter (ADC) using either analog ordigital gain control signals. These control signals steer the gain ofthe RF, baseband and possibly IF blocks. The gain is typically set bythe value of the received signal strength (RSS) at the received radiochannel, or by the total signal strength at the input of the ADC, usingsome specific algorithm. The gain control can be also based on the levelat the ADC input if a part of the channel filtering or despreading in aCDMA system is performed in the digital domain. All of these techniquesare well-known and are employed in many cellular receivers.

[0045] In addition to gain control, more sophisticated control methodshave also been presented for radio reception under dynamically changingconditions.

[0046] In general, the trade-off between power consumption and dynamicrange can be utilized to minimize the power consumption at each momentof time. Also, the modularity of base station applications could benefitfrom the use of a modular design. Often these techniques control thebiasing current or supply voltage of one or several receiver blocks.Referring also to FIG. 1 there are shown various prior art techniquesfor implementing adaptive reception in a receiver. These includeadjusting the biasing current to a device 1 (FIG. 1A), adjusting thesupply voltage of the device 1 (FIG. 1B), bypassing a stage (FIG. 1C),switching between stages (FIG. 1D), and switchable feedback (FIG. 1E).The power consumption can thus be scaled in various ways, such as byadjusting the bias current as in FIG. 1A, or by switching betweenparallel stages as in FIG. 1D, or bypassing certain devices that canalso be powered down (FIGS. 1B and 1C). The controlled device 1 can be asingle transistor, an amplifier, a mixer, a filter or any other activesingle component or multiple component circuit block in a radioreceiver.

[0047] Reference in this regard can be made to, for example, U.S. Pat.Nos. 5,179,724, 6,026,288 and 5,697,081, as well as to WO97/41643,WO00/18023 and EP0999649A2.

[0048] Overall control is normally based on one or several measuredparameters. These include the received signal strength (RSS), thesignal-to-interference ratio (SIR) (or its estimate at the detector),Ec/Io in CDMA systems (see U.S. Pat. No. 5,940,749, WO00/18023) and thetotal power at RF, IF or baseband (see WO97/41643). Also, interferingsignals can be estimated by measuring neighboring channels at separatemoments of time utilizing the same circuitry as the received signal (seeEP0999649A2). Intermodulation can be estimated separately by switching acontrollable attenuator into the signal path (see, for example, U.S.Pat. No. 5,907,798, U.S. Pat. No. 5,909,645, U.S. Pat. No. 6,052,566 andU.S. Pat. No. 5,697,081). Also, the known transmitted power can beutilized for power scaling in a receiver in those cases wheretransmission and reception occur simultaneously (see, for example, U.S.Pat. No. 5,815,821, WO99/45653 and WO00/18023.)

[0049] However, in general all of these techniques exhibit as a weaknessa requirement to make accurate estimates of the received signal and alsothe level of the total interference. Typically, the control is based onsome fixed thresholds that categorize both the received signal and theinterference to be either “weak” or “strong”.

[0050] One standard requirement in cellular communication systems is tomeasure the RSS. However, the RSS describes only the level of thereceived radio signal (over the channel bandwidth, for example) with acertain accuracy. It is also possible to estimate the SIR in the band ofinterest using well-known digital techniques, and the estimation of theSIR is currently a required measurement in some radio systems, such asin the 3G CDMA system. Unfortunately, the total interference arises fromseveral sources, which are very difficult or impossible to distinguishfrom one another based on conventional digital algorithms, in particularthose algorithms whose complexity would not be unreasonable to executein a mobile station employing its local computing resources. Forexample, the sources of interference in a CDMA system include at least:interference from other code channels of the same base station,interference from other code channels in the same frequency band fromother near-by base stations, interference from jamming signals, thermalnoise in the band of interest, as well as additional noise andinterference caused by the RF circuitry of the receiver itself.

[0051] The last factor, i.e., the additional noise caused by the RFreceiver circuitry, includes at least a noise figure (NF) of thereceiver, additional interference due to intermodulation and phase noiseof the oscillators in the receiver, additional noise due to intersymbolinterference (ISI) and, in digital radio systems, quantization noise.All of these are well-known phenomena in radio reception.

[0052] In full-duplex systems, where reception and transmission occursimultaneously (such as in CDMA systems), the undesired leakage of thetransmitted signal into the receiver can also cause a problem. Also,some receiver architectures have their own specific problems that giverise to additional interference, such as AM-distortion in directconversion receivers.

[0053] In any event, it should be appreciated that without intelligentlogic it is practically impossible to separate these different sourcesof interference and to determine their relationship to the SIR. As aresult, conventional radio receivers are designed to operate under theworst-case conditions by always operating at the maximum possibleperformance (and power consumption) level.

[0054] As was noted above, in conventional radio receivers it is knownto adjust the gain according to the RSS or signal level at the ADCinput. As the reception parameters typically change during operationwhen the gain control is applied, the power consumption is typicallyoptimized with respect to certain parameters such as the noise figure(NF), according to the worst-case scenario. Because the totalinterference cannot be predicted at each moment of time, additionalheadroom must be made available under typical operating conditions.Practically speaking, the gain control is required in all cellularsystems to extend the signal range of the desired channel at the inputof the receiver. However, a variation in the gain control does nottypically imply that the power consumption of the receiver is scaledaccordingly.

[0055] The gain and other receiver parameters are typically controlledusing logic based on the RSS and the total interference after thepreselection filter, or after some other filtering stage. Hence, thedecision is based on logic that does not indicate whether an out-of-bandinterferer will alias with a signal in the band of interest due tointermodulation. The out-of-band interferer(s) can thus be filtered outof the receive chain so that they can only degrade the performance dueto intermodulation, gain compression or desensitization, such as byraising the noise level or noise floor of the receiver circuitry. Hence,the estimate is based on information that does not have astraightforward relationship to the interference in the RF band ofinterest. In that the decision logic is typically based simply onthreshold values and thus gives, at best, only a coarse approximation ofthe receiving environment, the result is that certain receiverparameters can be set at levels that exceed what is required in theparticular receiving environment.

[0056] Only in certain limited cases can the interferer be defined withreasonable accuracy in advance. For example, the linearity of thereceiver can be increased using additional current when some knowninterference (normally due to TX leakage) exists in the system. In thiscase the logic can react only to a very limited number of conditionsand, typically, the receiver performance is made significantly betterthan what is actually required.

[0057] In conventional approaches it is also known that interferingsignals can be measured with the same receiver signal path as the actualreception signal path, but at the different moments of time. Forexample, in GSM there are mandatory measurements of other radio channelsthat can be measured, and their values can be used in the control logic.A switchable attenuator in the signal path can also be used to estimatethe ratio between intermodulation and other interference sources in theband of interest, as the slopes of the different non-ideal signalsdiffer as a function of signal power.

[0058] A combination of two or more of the foregoing techniques havealso been used in the prior art for receiver control purposes.

[0059] It should be noted that instead of the absolute signal levels(e.g., the RSS or the total power at some node), the SIR, or the SNR,or, in a CDMA system, the Ec/Io can be utilized as well by the receivercontrol logic.

SUMMARY OF THE PREFERRED EMBODIMENTS

[0060] The foregoing and other problems are overcome, and otheradvantages are realized, in accordance with the presently preferredembodiments of these teachings.

[0061] This invention describes an apparatus, a method and an algorithmfor controlling the dynamic range of a radio receiver. The algorithmuses a signal monitoring circuit that can measure simultaneously thetotal power due to intermodulation falling within a band of interestfrom all radio channels passing a preselection (a band selection) filterof a receiver circuit. In addition to the intermodulation product thealgorithm uses the received signal strength (RSS) and the total receivedpower passing the preselection filter to determine the requiredreception parameters for the receiver. Other available parameters, suchas the transmitted power level, may also be used. Based on thecalculated parameters the algorithm optimizes the power supply currentsand other controllable parameters of the receiver blocks such that therequired performance can be maintained under dynamic conditions, whileconsuming a minimum amount of power supply current.

[0062] This invention provides a monitoring circuit and associated logicto control the dynamic range of a radio receiver based on severalparameters, and thus makes it possible to continuously optimize thereceiver performance, for example, according to a minimum necessarypower consumption to obtain a desired quality of service (QoS). In thatthe amount of interference caused by different interference sources canbe distinguished from one other, the optimization of the receiverperformance can be accurately performed. The complete received spectrumpassing a preselection filter (band filter), and/or the LNA, is detectedwith the monitoring circuit and any intermodulation that falls in thereception band is separated from the blocking signal. If the detectioncan be made faster than the required control range requires, thedetector can be powered down momentarily to reduce the average powerconsumption.

[0063] These teachings enable different types of interference in the RFband of interest to be separated from one another. The measurements maybe performed continuously and at the same time as normal signalreception, without disturbing the normal signal reception. Themeasurements can also be accomplished discretely at certain moments oftime during signal reception, for example if fast, real-time control isnot required. All of the interfering signals can be detectedsimultaneously as the input to the detector is wide-band. However,narrow-band signal processing is preferably employed after the detectorto conserve power.

[0064] In accordance with these teachings a radio receiver can beprogrammed in substantially real time to operate with a minimumnecessary power consumption and, furthermore, the additional headroommay be reduced when the power consumption is optimized.

[0065] These teachings also make it possible to change the noise figure(NF) performance as compared to the use of RSS (or some other parameter)in those cases where the SIR or SNR requirement of the detected signalvaries. Such cases may be different data rates and quality requirements(BER or BLER), for example, between speech and data. These teachingsalso make it possible to reduce the quality of service (QoS), ifpermitted, in the case where the battery charge is low in order toextend the talk time or the stand-by time.

[0066] In CDMA systems where the capacity is limited by noise andinterference, and also by other transmitted channels in the RF band ofinterest, it is possible to trade-off between noise, interference andother code channels to achieve the required performance.

[0067] The use of these teachings also makes it possible to tunereceivers during production with a simple method to meet a particular RFspecification, even in those cases where the device under test willfail. The circuitry yields evidence of the possible problem, and bytuning the currents of the different receiver blocks in an appropriatemanner, the performance can be automatically tuned to meet the RFspecification.

[0068] It is important to note that the teachings of this invention gowell beyond the simple control of power consumption in one or severalreceiver blocks based on one or several measurements. This inventioninstead more particularly resides in a control method for a radioreceiver, rather than in a circuit technique to control the powerconsumption of any active circuit in the receiver. An important aspectof this invention includes a method to distribute the available headroomfor internal noise and distortion in the receiver between the noisefigure, the interference due to large signals (intermodulation andblocking) and other non-ideal signal reception conditions andoccurrences in an adaptive manner based on received signal strengthmeasurements and on the measured interferers. This invention alsoprovides a method that can utilize the information from different typesof interferences and combine them adaptively to optimize the performanceof the receiver to the currently received RF band (with respect to thepower consumption). The method employs a specialized signal monitoringcircuit that can separate input signals causing intermodulation tones inthe RF band of interest from other blocking signals, and also employslogic that can estimate the phase noise specification of the localoscillator by changing the input signal bandwidth of the signalmonitoring circuit.

[0069] These teachings thus provide a method for operating a radiofrequency (RF) receiver that executes, during operation of the RFreceiver, by periodically determining existing RF receiver operationalconditions; determining RF receiver performance requirements based atleast in part on the determined existing RF receiver operationalconditions; and by allocating power consumption between RF receiverfunctional blocks in accordance with the determined RF receiverperformance requirements and in accordance with a behavior model of atleast one of the RF receiver as a whole and individual functional blocksof the RF receiver. The method may also monitor the resulting RFreceiver signal quality to determine if allocation of power consumptionhas resulted in an optimum allocation of the power consumption.

[0070] Also disclosed is a communications device, such as a cellulartelephone or a personal communicator, that includes a RF receiver. Thedevice further includes monitoring circuitry, operable during operationof the RF receiver, for periodically determining existing RF receiveroperational conditions and for determining RF receiver performancerequirements based at least in part on the determined existing RFreceiver operational conditions. The device further includes powercontrol circuitry for allocating power consumption between RF receiverfunctional blocks in accordance with the determined RF receiverperformance requirements, and in accordance with a behavior model of atleast one of the RF receiver as a whole and individual functional blocksof the RF receiver.

[0071] The monitoring circuitry measures interfering signals anddetermines received signal distortion due to at least one ofintermodulation and blocking, and may also measure at least one of thereceived signal and internal conditions of a transceiver of which the RFreceiver is apart.

[0072] The monitoring circuitry operates to monitor a received signal inat least one of the RF, IF and BB sections of the RF receiver, wheremonitoring the received signal at BB can include making a measurement ofat least one of RSS, SIR, Ec/Io, BER and BLER.

[0073] In the presently preferred embodiment the monitoring circuitryoperates to determine at least one of: the gain of the RF receiver, acorrect value of the gain of the RF receiver, the noise factor of the RFreceiver, the third-order input intercept point of the RF receiver, thesecond-order input intercept point of the RF receiver, the inputcompression point of the RF receiver, and the phase noise of the RFreceiver.

[0074] The power control circuitry is responsive to resulting RFreceiver signal quality for determining if the allocated powerconsumption is an optimum allocation of the power consumption, andoperates by at least one of: varying at least one of the biasing currentand the power supply voltage, by bypassing at least one stage, byswitching between stages, and by changing feedback.

BRIEF DESCRIPTION OF THE DRAWINGS

[0075] The foregoing and other aspects of these teachings are made moreevident in the following Detailed Description of the PreferredEmbodiments, when read in conjunction with the attached Drawing Figures,wherein:

[0076] FIGS. 1A-1E, collectively referred to as FIG. 1, show prior arttechniques for implementing adaptivity in a receiver by adjusting thebiasing current, adjusting the power supply voltage, bypassing a stage,switching between stages and using switchable feedback, respectively;

[0077]FIG. 2 is a graph showing a minimum detectable signal in areceiver system (sensitivity) when the performance is dominated by (a)intermodulation and (b) blocking, where the x-axis represents theintermodulation or blocking power;

[0078]FIG. 3A illustrates the effect of a blocking signal and thepotential for channels to cause blocking in a CDMA system with 12 radiochannels, while FIG. 3B shows the effect of intermodulation and thepotential for channels to cause interference due to intermodulation in aCDMA system with 12 radio channels, where in both examples the receivedchannel is assumed to be located in the lowest frequency band, thepotentially interfering signals are shown in solid black, and the otherchannels are shown in white;

[0079]FIG. 4 is a logic flow diagram that illustrates the receiveroperational control principle in accordance with this invention;

[0080]FIG. 5 is a block diagram of an adaptive receiver that includesthe control logic in accordance with this invention, wherein a directconversion receiver architecture is shown by example but not by way of alimitation;

[0081]FIG. 6 is a logic flow diagram that illustrates an algorithm formonitoring the total power, the intermodulation power and the power nearto the RF carrier frequency;

[0082]FIG. 7 is a logic flow diagram that illustrates an algorithm forcalculating the receiver performance requirements;

[0083]FIG. 8 is a graph that illustrates the maximum noise figure of areceiver IC with linear and parabolic equations, where the parameterk=0.5 is used in the linear model and the parameter m=0.1 is used in theparabolic model;

[0084] FIGS. 9A-9E, collectively referred to as FIG. 9, illustratebehavioral models for certain receiver parameters as a function of powerconsumption: specifically gain, noise figure, IIP3, noise figure withprocess variations (dashed lines) and noise figure with differentblocking signal levels, respectively;

[0085] FIGS. 10A-10C, collectively referred to as FIG. 10, illustratepower consumption requirements for examples A, B and C from the NF andIIP3 perspective, where the required power consumption can be chosen tobe the minimum necessary that meets both conditions;

[0086] FIGS. 11A-11L, collectively referred to as FIG. 11, show a numberof mathematical expressions that are solved during the execution of thealgorithm shown in FIG. 4 or during the generation of the lookup tablethat maps the measurement to the receiver control in accordance with thealgorithm;

[0087]FIG. 12 is a graph that illustrates an example of the IIP3specification as a function of IMD3 source power for different RSSlevels, where a parabolic noise figure model has been used in thecalculations;

[0088]FIG. 13 is a graph that illustrates an example of the IIP2specification as a function of IMD2 source power for different RSSlevels, where the parabolic noise figure model has been used in thecalculations;

[0089]FIG. 14 is a circuit diagram showing a presently preferredembodiment of an intermodulation detector that forms a part of thesignal monitoring block shown in FIG. 5;

[0090]FIG. 15A is a logic flow diagram that illustrates a technique fordynamically tuning a receiver; and

[0091]FIG. 15B is a state transition diagram for a receiver systemundergoing dynamic tuning in accordance with the logic flow diagram ofFIG. 15A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0092] In accordance with an aspect of these teachings theintermodulation products that can be aliased in the RF band of interestare separated from other sources of interference. A presently preferredalgorithm estimates the role of intermodulation in the systemperformance separately from other sources of interference. This isachieved by using a circuit that can detect the components arising fromother interfering signals. In the presently preferred embodiment thiscircuit is one described by Pauli Seppinen, Aarno Pärssinen and MikaelGustafsson, “Intermodulation Detector for a Radio Receiver”, U.S. patentapplication Ser. No. 10/034,643, filed on even date herewith andincorporated by reference herein, although the circuit is not limited toonly this particular one.

[0093] In many cases the power consumption of the receiver, or oneparticular block in the receiver, is dominated by the intermodulationdue to the third-order nonlinearity that is inherent in the systemspecification. Such a situation is, however, rare in a practicalembodiment, in spite of a relatively stringent requirement for thethird-order input intercept point (IIP3) given in the systemspecification (defined for the worst case condition.) Therefore, undermost operating conditions the receiver performance exceeds what isactually required.

[0094] Compression and desensitization are other parameters in the radioreception that are related to the large signal environment. However,their consequences are different from a system perspective. Compressionand desensitization result from a single large blocking signal or thetotal signal power passing through a nonlinear device. In general,compression reduces the gain of the circuit and desensitizationincreases the noise in the circuit. Hence, in the blocking situationboth effects reduce the dynamic range. On the other hand,intermodulation (IIP3) brings undesired signals from other radiochannels into the band of interest. The effect is more serious than thatresulting from blocking as smaller signal levels can cause anunacceptable degradation in the performance of the receiver, as comparedto blocking. It has been estimated that in certain cases the blockingpower may need to be over 15 dB greater than the intermodulation powerin order to cause the same degradation in sensitivity. This differenceis illustrated in FIG. 2, which shows the minimum detectable signal inthe system (sensitivity) when the performance is dominated by (a) theintermodulation, and (b) blocking. The x-axis presents theintermodulation or blocking power.

[0095] However, intermodulation requires a certain combination offrequencies, f(RF)=2(f(D1)−f(D2)), where f(RF) is the frequency of thedesired signal and f(D1) and f(D2) are the frequencies of the twoundesired signals causing distortion, while blocking can be caused byany signal or combination of signals passing the preselection filter, asshown in FIG. 3. More specifically, FIG. 3A illustrates the effect ofthe blocking signal and potential channels to cause blocking in a CDMAsystem with 12 radio channels, while FIG. 3B shows the effect ofintermodulation and potential channels to cause interference due tointermodulation in a CDMA system with 12 radio channels. In bothexamples the received channel is located at the lowest frequency band,the potentially interfering signals are marked in solid black and theother channels are marked in white.

[0096] Hence, it can be appreciated that if the decision is based onlyon one of the previous two parameters the performance cannot be uniquelyoptimized due to the different effects from the system point of view.Also, it should be appreciated that although at least theoretically acertain relationship exists between compression and intermodulation, thetwo nonlinear phenomena can be dominated by different devices in thereceiver. Hence, the relationship between blocking and intermodulationdepends as well on the circuit topology, and the optimum performance ispreferably estimated accordingly.

[0097] Because the intermodulation power is separated from the blockingpower by the application of the teachings of this invention, it becomespossible to use less current in the receiver at any time when arelatively large blocker exists, but the frequency combinations at theinput of the receiver do not produce intermodulation products in the RFband of interest.

[0098] The internal optimization is preferably accomplished using abehavioral model for each receiver block, and the total receiverperformance is then determined from the models of the separate receiverblocks. A discussion of the presently preferred behavioral models ismade below.

[0099] It should be noted that the receiver performance model may alsobe defined from the simulated or measured results of the entire receiveras well.

[0100] The teachings of this invention pertain to a control method for aradio receiver that utilizes at least one signal monitoring circuit atRF, IF or analog baseband, or at digital IF or baseband, that canseparate different types of interference, that employs measurements doneat the digital baseband, as well as logic to calculate the receiverparameters from the measurements and known system conditions, logic todefine an optimal power distribution between receiver blocks toaccomplish the necessary receiver parameters using behavioral models ofthe receiver and/or individual blocks, and control logic to adjust thepower consumption of the different blocks in the receiver using, forexample, techniques such as those illustrated in FIG. 1. The overallcontrol method is shown in FIG. 4, and a block diagram of an adaptivereceiver according to the invention is shown in FIG. 5. While a directconversion receiver architecture is used for the illustrated example ofFIG. 5, the teachings of this invention are not limited for use withonly direct conversion architectures, and systems that generate one ormore Intermediate Frequencies (IFs) can use the teachings of theinvention as well, such as superheterodyne or other receiverarchitectures. The nodes N1, N2, N3 and N4 from which the signal ismonitored by signal monitoring block 10 are examples of potential nodes,and should not be viewed in a limiting sense. In the simplest form onlyone measurement node is required, and a presently preferred mode forimplementation is to make the measurements at RF at the node N2 betweenthe low noise amplifier (LNA) 12 and the downconversion mixer 14. Thereceiver in FIG. 5. contains in-phase (I) and quadrature (Q) channels,and for simplicity only the blocks of the Q channel are shown as beingcontrolled. However, it should be apparent to those skilled in the artthat both the I and the Q channels should be controlled in the samemanner. Also, the monitoring circuitry 10 can be connected either to onechannel or to both channels simultaneously. In FIG. 5, the RXperformance control logic 20, RX block control logic 22 and thebehavioral models 24 are drawn as separate blocks to improve theclarity. However, they can all be combined in a practical implementationinto a common logic block. The three blocks 20, 22 and 24 are employedto implement the teachings of this invention, in addition to the signalmonitoring circuitry 10 that can separate intermodulation from blocking.In the presently preferred embodiment the intermodulation detectioncircuit is the one referenced above as being described by PauliSeppinen, Aarno Pärssinen and Mikael Gustafsson, “IntermodulationDetector for a Radio Receiver”, U.S. patent application Ser. No.10/034,643, filed on even date herewith and incorporated by referenceherein in its entirety. An overview of this circuit is described belowin relation to FIG. 14.

[0101] For completeness, FIG. 5 also shows a receive antenna 4, an inputbandpass (preselection) filter 6 and a balun 8 that feeds the LNA 12.The downconversion mixers 14 receive their mixing frequencies from alocal oscillator (LO) that includes a synthesizer 30, voltage controlledoscillator 32, buffer 34, divide by two block 36 and further buffers 38.The outputs of the downconversion mixers 15 are applied to variable gainamplifiers 15, low pass filters 16, second variable gain amplifiers 17,analog to digital converters ADCs 18, baseband low pass filters 19 andchannel decoders 28. A baseband (BB) systems measurement block (RSS,SIR, etc.) 26 generates an output signal that is applied to the RXperformance control logic 20, in combination with the output from thesignal monitoring block 10. The RX performance control logic block 20generates values for NF, Av, IIP3, ICP, Nph, and possibly othercontrols, and outputs these values to the RX control logic block 22. TheRX control logic block 22 in turn controls the various receiver blocks,in cooperation with the output of the behavioral models block 24.

[0102] The operation of the individual process blocks in FIG. 4 will nowbe described. Preferably, but not necessarily, the control procedure isexecuted once during one time slot during radio reception.

[0103] The method starts at Step A, and at Steps B and C the methodmonitors interfering signals and measures the received signal. Morespecifically, at Step B the signals can be monitored at RF, at IF (ifthe receiver has an intermediate frequency) and/or at BB. The signalmonitoring in this context means all possible signal monitoringtechniques that can be done before the channel selection filtering. Thepreferred node to monitor for undesired signals is before the RF mixer14 (or with a system having wide-band IF processing also at the outputof the mixer). This location is preferred for two reasons. First, thepreceding RF amplification by the LNA 12 relaxes the gain requirementsof the monitoring circuit 10, but does not limit the band of possibleinterferers significantly. Second, after the RF mixer 14 the band istypically filtered in blocks 16 in the direct conversion architecture torelax the linearity requirements of the baseband blocks. Hence, widebandpower detection becomes impossible after the lowpass filteringoperation. In the superheterodyne architecture a significant bandlimitation occurs at the IF (meaning the first IF if there are severalintermediate frequencies). Therefore measurements in a superheterodynereceiver are preferably performed before the first IF filtering toachieve reliable results with the best sensitivity for RF optimization.

[0104] Analog signal monitoring can be done with one or severaldifferent monitoring circuits and separate monitoring circuits can beused to monitor different types of interferers. For example, theintermodulation and the total power can have different monitoringcircuits. However, to minimize the circuitry and silicon area in theimplementation the preferred mode is as follows. One monitoring circuit(signal monitoring block 10) is connected at the input of the RF mixers14 is used that can measure both the total power and the intermodulationwith a simple configuration step between modes. Hence, these twomeasurements are not done simultaneously, but assuming that theswitching between modes can be done fast enough both measurements can beperformed with sufficient accuracy even in fluctuating signalconditions. The required switching between modes can be done mostoptimally according to FIG. 6. The downconversion to baseband signal isnot shown in the algorithm description. There is an option to measurealso the frequency difference of the blocking signal from the frequencyof interest. This option can be used in the scaling of the LO signalpath power (VCO 32, dividers 36, etc.) as will be discussed later. InFIG. 6, the parameters Ptot and IMDtot describe the total power and theinterfering power due to intermodulation at the input of the monitoringcircuit 10, respectively. Ptot_LOW describes the threshold value underwhich interfering power levels are insignificant for the systemperformance. This level is defined based on the sensitivity of the powerdetector and the algorithm that is used. The power Pnw describes thetotal power that is close to the received carrier frequency, after theinput bandwidth of the monitoring circuit 10 is reduced to the bandwidthgiven by the f(nw). The use of this measurement with the reducedbandwidth around the RF carrier frequency is described in further detailbelow.

[0105] At Step C the algorithm measures the received signal at BB.Different parameters describing the radio link, such as the RSS or theSIR, can be defined using digital signal processing. Many cellularsystems require certain measurements be made with a certain accuracy.The parameters defined at digital baseband and used in this inventioncan be acquired with conventional digital techniques. The receivedsignal strength (RSS) is a presently preferred mandatory parameter inthe method, while the SIR, or actually its estimate, is a usefuloptional parameter when estimating the performance changes. This is truebecause of the adaptivity. The Ec/Io is a parameter related to CDMAsystems and describes the amount of signal power compared to other codechannels and interference in the RF band of interest. The bit error rate(BER) or block error rate (BLER), if available in the system, can bealso used in the method. However, with these parameters it is onlypossible to estimate long term changes in the reception conditions andtherefore they are impractical to use in most cases. Also, otherparameters may be available in the system. Besides of RSS all of theother parameters are optional for use by the algorithm, but their use ingeneral improves the accuracy of the result.

[0106] At Step D the method calculates the receiver performancerequirements. A presently preferred algorithm for this purpose is shownin FIG. 7. An evaluation is first performed as to whether any measurablesignal exists in the signal monitoring circuit 10 (or if the signal isabove a certain threshold limit). If no interference is observed thenoise figure requirement of the receiver is calculated using a small orno margin as compared to a minimum required NF. The calculation of thenoise figure is explained in further detail below. Then the requirementsof IIP3, ICP, Nph and possibly other receiver parameters that arerelated to large interferers are set to the values that meet therequirements of the smallest measurable interfering signal level.

[0107] In the case where large interfering signals occur, the noisefigure requirement is calculated such that the internal noise of thereceiver only reserves a part of the additional headroom in thesignal-to-interference ratio (SIR), and the remainder of the acceptableinterference can be caused by IIP3, ICP or other receiver non-idealcharacteristics. The NF, IIP3 and ICP requirements can be calculated asshown below. In direct conversion receivers the second-order inputintercept point (IIP2) is also significant. The requirement for IIP2 canthus also be calculated. However, the IIP2 requirement is handledseparately because of the completely different tuning mechanisms. IfIIP3 and ICP requirements are higher than the maximum achievable withthe current receiver (IIP3_max & ICP_max) it is possible to reduce thenoise figure requirement and, hence, increase the margin between theinternal noise and the maximum acceptable interference.

[0108] The phase noise (Nph) requirement for the local oscillator LO (orLOs depending on the receiver architecture) can be calculated based onthe total power (Ptot) and/or on the undesired power close the RFcarrier (Pnw). There is a certain maximum acceptable phase noise (Nph)for the reception of a modulated channel, which is the limit value whenlarge interferers do not exist. However, it is possible to calculate thephase noise requirement for the local oscillator and the other circuitry(dividers 36, buffers 38, etc.) between local oscillator and mixer 14 LOports as a function of Ptot or Pnw. Because the phase noise is afunction of the power consumption, the total power consumption of thereceiver can be scaled according to the phase noise requirement. Bymeasuring the nearby interferers Pnw it is possible to improve theaccuracy of the algorithm as the phase noise requirement is reduced as afunction of the distance in frequency between received channel and theinterfering signal. The phase noise calculation can be performedindependently of the IIP3 and ICP characterization, and therefore theirorder can be changed. However, both parameters add interference and thussome headroom should be reserved for the other parameter when the firstrequirement is defined.

[0109] The calculations for NF, IIP3, ICP, IIP2 and Nph can be performedaccording to the examples given below. However, these calculation shouldonly be considered as the presently preferred best mode of operation asother mathematical formulas may be developed to yield the same orsimilar information within the system. Also, other receiver parameterscan be specified, although those described are believed to be the mostsignificant ones.

[0110] The system specifications in an adaptive system are preferablydefined separately for each reception condition. Those parameters thatcan be used at these occasions are, for example, the received signalstrength (RSS), the total power at the input of the receiver(P_(block)=P_(tot)) and the power causing third-order intermodulation(P_(IMD3,source)). The information of the other code channels in thereception band in a CDMA system can also be useful.

[0111] What follows is now a more detailed description of the variouscalculations that are performed in accordance with the algorithmillustrated in FIG. 4, and in the algorithms shown in FIGS. 6 and 7 thatare constituent parts of the algorithm of FIG. 4. Reference is also madeto FIG. 11.

[0112] NF

[0113] The maximum noise figure (NF) can be defined for each input levelaccording to the expression shown in FIG. 11A, where NF_(RX) is thenoise figure of the receiver at the antenna 4 connector, SNR_(min) isthe minimum required signal-to-noise ratio for detection and N_(TH) isthe thermal noise in the band of interest i.e. N_(TH)=10*log(kTB)=−174dBm/Hz+10*log(B). B is the bandwidth of the received channel. Allnumbers are given in decibels. The maximum noise figure for the systemat a sensitivity level can be calculated by setting the sensitivity asRSS. The loss of the components that precede the LNA 12 (or IC) in thereceiver are taken into account when calculating the IC requirements.Typically the loss is dominated by the preselection filter 6 or theduplex filter. Hence, the IC NF requirement can be given by theexpression shown in FIG. 11B, where L_(duplex) models the total lossbetween the antenna 4 connector and the IC that embodies the circuitryshown in FIG. 4.

[0114] In a radio system specification noise is typically the onlyparameter that causes interference to the signal when the input signalis at the sensitivity level. Therefore NF_(IC)+N_(TH) and NF_(RX)+N_(TH)should be considered as the maximum interference level at the band ofinterest (D_(TOT)), including noise and distortion of the receiverblocks as well as interference from other code channels in a CDMAsystem. The NF typically dominates the performance only close to thesensitivity level. It can be specified to be less at higher signallevels to allow some headroom for nonlinearities and other distortion,which normally dominate the performance. This headroom can be used whenspecifying other parameters. Hence, a linear or a parabolic equation forNF specs at the input of the IC can be calculated. An example of alinear function is shown in FIG. 11C, where MDS is the minimumdetectable signal (sensitivity), NFIc.N)s is the noise figurespecification at the sensitivity level and k is the slope of thespecification, which can be defined by the system designer. All numbersare again in decibels. A typical system specification requires that,with out-of-band interferers, the specification is defined when thereceived signal is 3 dB above the sensitivity threshold. In order not todisturb that specification 3 dB is subtracted in the equation in FIG.11C. Below that point noise should be considered constant and theequation is not continuous.

[0115] A hyperbolic function, which avoids this problem, can be readilydefined, and also more closely resembles the properties of a typicalreceiver chain at different gain control values. However, the algorithmmay be more difficult and power consuming to realize. The specificationcan then be given in accordance with the equation shown in FIG. 11D,where the parameter m can be selected by the system designer. Themaximum noise (and distortion) level, and the two mathematical models asa function of RSS, are shown in FIG. 8 for a WCDMA system. Similarcalculations can be done for other types of radio systems as well.

[0116] IIP3

[0117] The maximum third-order input intercept point (IIP3) can bedefined from the noise figure and from the total acceptableinterference. The total interference can be found in accordance with theequation of FIG. 11E, where P_(IMD3,m) is the third-order interferencereferenced to the input of the receiver. Both NF and P_(IMD3,m) arefunctions of RSS. The maximum acceptable total interference is definedby the RSS and the minimum required signal-to-noise ratio (SNR_(min))for the current signal quality requirement in the reception as shown inthe equation of FIG. 11F. Hence, the maximum level of the third-orderinterference can be given by the expression of FIG. 11G.

[0118] The specification for the IIP3 can thus be calculated inaccordance with the equation shown in FIG. 11H, where P_(IMD3,source) isthe power at the input causing distortion due to third-orderintermodulation. The IIP3 specification for the noise figurecharacteristics given by the parabolic function is given for differentsignal levels (RSS) in FIG. 12.

[0119] If there are some other potential non-ideal signal conditionsthen some certain amount of headroom can be reserved for them as well inthe expression of FIG. 11G. Hence, it should be realized that theoptimization can be done in the same manner using more than twoparameters, such as NF and IIP3 as in this example.

[0120] IIP2

[0121] A similar model as for IIP3 can be also defined for IIP2.However, the amount of amplitude envelope or envelope distortion is moredifficult to define than is the intermodulation power. If it is assumedthat IIP2 behavior is dominated by a modulated channel havingnon-constant envelope, the virtual source power (P_(IMD2,source)) can bedefined as shown in equation 11I, where P_(block) is the average powerof the distortion (e.g., in a modulated channel), ΔP_(AM) is therelative amount of amplitude modulated power in the signal given in dBcand P_(outband) is the power, which aliases out-of-band during squaringof the signal. Hence, P_(outband) is approximately 3 dB in the case ofsecond-order distortion. When specifying several distortion parametersfor the receiver their relations should be defined as was done betweenthe noise and the IMD3 distortion earlier. In the case of second-orderdistortion it may be preferable to ‘overspecify’ the performance inorder to conserve headroom for the other parameters. Of course that canbe done only if the parameters can be defined independently, at least tosome extent, and only if the maximum requirement is feasible. This isdone here by defining the maximum envelope distortion, referred to theinput, as shown in equation 11J, where D_(TOT) is the total interferenceas was defined earlier and ΔP_(IMD2) is the difference in dB. If thedifference is set to, for example, 10 dB, the second-orderintermodulation distortion can be only 10% of the total amount. In thatcase, relatively small headroom should be reserved for the otherparameters in the implementation. The specification for IIP2 can thus bewritten as is shown in the equation of FIG. 11K. IIP2, as a function ofIMD2 source power, is shown in FIG. 13 in a similar manner as IIP3 wasshown in FIG. 12. The selectable parameters in this example are:ΔP_(IMD2)=10 dB, ΔP_(AM)=10 dB and P_(outband)=3 dB.

[0122] ICP

[0123] The input compression point (ICP) is related to the othernonlinear effects in the receiver circuitry, and a most simplifiedanalysis gives a theoretical result that ICP is 9.6 dB lower than IIP3when only a single non-linearity dominates in an active circuit.However, in practice the difference is typically between 5 and 15 dBs inRF circuits. IIP3 and ICP cause different mechanisms to deteriorate thesignal and therefore their separation may be desirable. The ICPrequirement can be calculated separately, and the logic can estimatewhether IIP3 or ICP sets the more stringent requirements for thereceiver performance and can thereby adjust the receiver accordingly.

[0124] The compression of the gain due to the presence of a largeblocker (P_(block) or measured P_(tot)) can be defined as a function ofthe interfering power i.e. A_(v)(P_(block)), where A_(V) is the gain ofthe receiver. Because the gain compression is related to the powerconsumption of the receiver the blocking power (i.e. measured totalpower) can be directly used to calculate the required power consumptionof the receiver and to tune the different blocks of the receiver to meetthis specification.

[0125] The presence of a large blocking signal also increases the noisein the active circuits. Therefore the noise figure of the circuit is afunction of the total power. However, relatively large signal levels areneeded before the effect becomes significant. It is possible tocalculate the noise figure specification, as was shown above, by takinginto account the blocking signal, i.e. NF_(RX) is a function of RSS andP_(block), NF_(RX)(RSS,P_(block)). Then the other parameters such asIIP3 are calculated in accordance with the more stringent requirements.Another option is to calculate the additional noise caused by theblocker and to then compare it to other interferences. In this case thetotal interference D_(TOT), which can be compared to the received signal(RSS), can be expressed as shown in the equation of FIG. 11L, whereN_(RX)(P_(block)) is the additional noise that results from the presenceof the blocking signal.

[0126] Phase Noise

[0127] The phase noise specification can be calculated from the receivedsignal strength (RSS), from the total blocking power (P_(block)=P_(tot))and/or from the measured interfering power levels that are located closeto the desired carrier frequency (P_(nw)). The maximum acceptable phasenoise N_(ph,max) depends on the requirements of the demodulation of thechannel. That requirement is significantly relaxed compared to thesituation when the phase noise mixes with a large interferer close bythe desired carrier. In the latter case, a part of the phase noise willbe aliased over the band of interest, thereby further deteriorating thereception. This requirement is one of the strictest from theimplementation point of view in several radio systems and therefore isextremely critical for the power consumption. Hence, the phase noiserequirement is preferably input to the receiver power consumptionoptimization logic when it is defined as a function of blocking power,i.e., N_(ph)(RSS,N_(ph,min), P_(block) and/or P_(nw)). Additionalheadroom is preferably reserved for the phase noise if the distancebetween the received carrier and a large undesired interferer is notknown.

[0128] The receiver behavior model(s) 24 are now described in furtherdetail. The required performance parameters are mapped into the receiverperformance using logic. Therefore the receiver performance parametersare preferably defined as a function of current consumption over theentire operational range. First, the required parameters and scalingpossibilities are defined for each individual receiver block separately.Then the total performance is defined by combining the different blocks.The parameters for each individual block may be determined either bysimulations or by measurements, and the combination of the differentblocks may be accomplished by simulations, calculations, or bymeasurements. All of these methods are generally known in the art.However, the large number of parameters makes the optimization verydifficult, and the optimization is therefore preferably performed by adifferent technique. The behavioral model can be similar to all devices(receivers) implemented for the same system and defined beforehand, orit can be modified during fabrication or operation individually for eachdevice to optimize the performance from the system perspective takinginto account also process variations etc. The behavioral modelpotentially has a large number of different options for implementation,and all of these options may be used by the teachings of this invention.Therefore only a relatively simple behavioral model for the receiver isnow described, which is also a presently preferred embodiment. Thepreferred model is one for the entire receiver. However, the model canbe partitioned between a plurality of receiver functional blocks, andthe logic to distribute power consumption can include an algorithm forinternal optimization. Therefore the border between these two blockslabeled as E and F in FIG. 4 should be viewed as being flexible.

[0129] FIGS. 9A-9E, collectively referred to as FIG. 9, illustratebehavioral models for certain receiver parameters as a function of powerconsumption: specifically gain, noise figure, IIP3, noise figure withprocess variations (dashed lines) and noise figure with differentblocking signal levels, respectively. It is neither necessary todescribe all of parameters given earlier, nor are the absolute valuesrequired to describe the behavior. The relationship between powerconsumption and certain parameters is one that should be known andunderstood by one skilled in the art. Instead of the complete receiverthe performance parameters can describe also one single block or a groupof the receiver blocks. The effect of process variations on theimplementation is described in FIG. 9D. If the calibration orverification step cannot be performed (Step H of FIG. 4), the algorithmpreferably assumes the worst case condition for each parameter. If theactual performance as a function of a certain parameter can be definedor calibrated the actual value of the particular device (or receiver)can be used. FIG. 9E shows the noise figure as a function of powerconsumption at three different blocking levels. Using this model thereceiver noise figure (NF) can be optimized in the presence of ablocking signal.

[0130] The logic block 22 that distributes the power consumption betweenthe different receiver blocks can either use the behavioral model forthe entire receiver, or it may use, for example, separate behavioralmodels for the signal path and LO path, or it may use behavioral modelsfor each receiver block individually. Combinations of these can also beused. In the first case, the logic block 22 determines the minimumnecessary power to achieve the required performance parameters accordingto existing reception conditions. A simple example for three differentcases is shown in FIG. 10. In FIG. 10A, a high linearity and arelatively low noise figure are required. However, the linearityrequirement clearly sets the power consumption. In FIG. 10B thelinearity requirements are relaxed and the noise figure (NF) is thelimiting factor for the power consumption. In FIG. 10C both parametersare relaxed, but NF is still the limiting factor. This example shows amethod in which the receiver performance is already defined as afunction of total power consumption, and a fixed power distributionbetween blocks is selected beforehand. It is a straightforward approachand allows the use of lookup tables. However, more complex methodscapable of yielding improved optimization results with lower powerconsumption are also possible to implement using this method. Theexample of FIG. 10A may be considered as a requirement imposed by acertain specification or standard, while the case of FIG. 10C may be thetypical case in a fluctuating signal environment.

[0131] Although the changes in signal levels are preferably relativelysmall,,the logic 22 that issues the commands to the active circuits mayalso have knowledge of conditions that relate to the previous state ofthe receiver. This may be desirable, for example, when signal transientsdue to the control of the receiver may cause a disturbance to thereceived signal. Such logic then rules out impossible transitionsbetween certain states, although these transitions may be the bestalternatives strictly from the power consumption point of view.

[0132] Referring now to Step G of FIG. 4, different blocks in thereceiver can be controlled by adjusting the supply current or the supplyvoltage or by some other technique as described in detail above withrespect to FIG. 1. While this invention may employ any suitable controltechnique, in most cases it will be found that the most effective way tocontrol the RF and analog circuits is to steer the supply current.

[0133] The power control of the receiver blocks receives the commandsfor each individual block from the power distribution logic 22 (e.g.,ctrl_LNA, ctrl_VCO, ctrl_synth) and performs the commanded changes atthe desired points in time. Synchronization to the digital signalprocessing block of the receiver is generally not necessary, but in somecases may be desirable.

[0134] The signal quality can optionally be checked in Step H of FIG. 4by comparing, for example, the estimated SIR before and after the powercontrol of the receiver blocks. There should not be any significantdifference in the results if the receiver parameters do not dominate theinterference. In that case the tuning is definitely acceptable. However,if the receiver parameters have significant contribution to SIR it ispossible to estimate whether the SIR remains at an acceptable levelafter the tuning, i.e., SIR_est>SIR_min, where SIR_min is the minimumacceptable level for the detection. Also, other parameters such as BER,BLER, error vector magnitude (EVM) or cyclic redundancy check (CRC) thatcan be defined in the receiver can be used in a similar manner toestimate the minimum acceptable signal quality during the reception.

[0135] This step is optional as it is possible to define a sufficientamount of headroom for different receiver parameters in order to avoid asituation in which the power consumption tuning can significantlydeteriorate the reception. However, an optimal algorithm will minimizethe extra margin in the performance, and therefore some mechanism tocheck the signal quality can be desirable to provide.

[0136] Reference is now made to FIG. 14 for showing a presentlypreferred embodiment of the signal monitoring circuit 10, in combinationwith another view of the RF receiver. The signal monitoring circuit 10,also now referred to as an intermodulation detector (IMD) 10, operatesin parallel with the radio receiver and can provide to the receivertuning logic module signals useful in tuning the radio receiver. Theintermodulation detector 10 is essentially a receiver made to beespecially sensitive to intermodulation distortion. Using as an input adetector signal derived by the receiver from the received signal, theintermodulation detector 10 provides two signals: a first signal P_(WB)indicating the total power at the input of the receiver detected beforeor after the first amplifier (LNA 12 in FIG. 5) and a second signalP_(IMD3) indicating essentially the cubed value of the signals fallingonto the channel to which the receiver is being tuned (the phenomenonoccurring because of the detection of the input signals causingnon-linear components in the receiver perceived by the intermodulationdetector, and not necessarily occurring to the same extent in thereceiver). Another unwanted effect in the receiver under largeinterfering signals is compression. A large signal in the receiver cancompress the gain of the signal path through blocking or increasing thenoise in the signal path due to changing the operation conditions ofanalog circuits. The measurement of wideband power by squaring asindicated in FIG. 14 well known in radio reception. However, thewideband signal taken (tapped) from the node between mixers 71 and 72 isa very useful parameter for the optimization of the radio receiver andtherefore has separate output lo from the intermodulation detector.

[0137] The aliasing onto the channel to which the receiver is beingtuned occurs because of the detection of the potential sources causingnon-linear components in the intermodulation detector, and notnecessarily occurring to the same extent in the receiver. Theintermodulation detector 10 is essentially a monitoring circuit for aradio receiver that can collect nonlinear components, which will aliasonto the channel to which the radio receiver is tuned, with linearoperations in a controllable manner from a wide band of frequencies. TheIMD circuit 10 is designed to be more sensitive to intermodulation thanthe actual received signal path and, hence, it can indicateintermodulation sources before they significantly disturb the radioreception. If two strong signals outside of the channel to which theradio receiver is being tuned pass through-non-linear circuits in aradio receiver, and the difference in the frequencies of the two tonesis certain, then the two channels are said to produce an intermodulationsignal that aliases onto the channel to which the radio receiver isbeing tuned. The two signals provided by the intermodulation detector10, the (measured) intermodulation distortion P_(IMD3) and the(measured) total power P_(WB), can be used to adjust the linearity ofthe radio receiver 10, as well as for the purposes of this invention.

[0138] In FIG. 14, besides the signal at the band of interest, there areseveral other radio channels at different carrier frequencies to whichthe antenna responds, i.e. the intermodulation detector 10 has a widerinput bandwidth than the received channel. Those channels can cause theunwanted intermodulation products aliased to the band of interest if thesignals are strong enough. Note that the intermodulation detector 10 isnot connected directly to the input of the radio receiver; instead, inthe best mode, it measures the signal at the node (i.e. taps the signalat the node) between LNA 12 and mixers 14 (although the measurementswith the same intermodulation detector can also be performed by tappingthe input of the LNA 12). The intermodulation detector 10 can be used inother radio receiver architectures besides the direct conversionarchitecture indicated for the radio receiver of FIGS. 5 and 14, and sothere are also other nodes in a radio receiver where measurements can bemade by the intermodulation detector 10. Also, if there is a need todetect the total power or intermodulation power from a narrower bandthan will be downconverted with mixer 76, the measurement bandwidth canbe limited either at the output of mixer 76 or at the input of mixer 71with conventional techniques. Such a technique can be for example anadditional capacitor connected between the signal ground and theparticular node. In addition, the capacitor can be tuned or switchedduring operation according to prior art design techniques, making itpossible to observe whether the source of distortion (either total poweror intermodulation) is close to the carrier in which the receiver isbeing tuned. Such information can be utilized in the receiver tuninglogic if needed.

[0139] In the implementation shown in FIG. 14, the intermodulationdetector 10 takes as input the wideband signal received by the radioreceiver after it is amplified by the LNA 12, and mixer 76 mixes thewideband signal with a sinusoid provided by LO 32. The local oscillator32 provides a signal at the frequency to which the radio receiver istuned, and so the mixing of the carrier signal and the received signalproduces a signal that, when highpass filtered using highpass filter(HPF) 77, no longer includes the frequency to which the radio receiveris tuned. The signal, after highpass filtering, is then provided tomixer 71 where it is mixed with itself, so that it is squared, andtherefore provides a measure of the power of the received signalexcluding the power at the frequency to which the radio receiver istuned. In an optional branch of the intermodulation detector 10 theoutput from the mixer 71 is provided to a subsystem 704 b for generatinga digital signal indicating P_(WB). In the P_(WB) subsystem 704 b, theoutput from the mixer 71 is provided to an amplifier 78 that can beeither a linear amplifier or a logarithmic amplifier (indicated as aLin/Log amplifier 78). The output of amplifier 78 is lowpass filteredusing a lowpass filter (LPF) 79 and converted to digital form by an ADC80, thus providing a signal P_(WB) indicating the power of the receivedsignal, excluding the power at the frequency to which the radio receiveris tuned.

[0140] In the main part of the intermodulation detector 10 the output ofmixer 71 is also provided as an input to a further mixer 72, where it ismixed with the original output of the highpass filter 77, and soproduces as an output essentially the cube of the signal provided by thehighpass filter. The cubed output is then processed by a subsystem 704 afor providing a digital signal indicating the intermodulation power atthe frequency to which the receiver module is tuned. In the subsystem704 a, the cubed output is low-pass filtered by a LPF 81, then amplifiedby an amplifier 82, indicated (detected) by squaring it using a mixer73, and lowpass filtered again, using another LPF 83. The result isconverted to a digital signal using ADC 84, yielding a digital signalP_(IMD3) indicating the intermodulation power at the frequency to whichthe radio receiver module 10 is being tuned.

[0141] The detector circuit branch including mixer 73 and the lowpassfilter 83 and ADC 84 following the mixer 73 are just one example of animplementation for providing a signal indicating P_(IMD3) The functionof this circuit branch can of course be accomplished using otherimplementations, such as for example one in which the mixer 73 isreplaced with a digital mixer placed after the ADC.

[0142] The methods described above can be implemented with customizedlogic on the same die with any of the analog circuits, or on amixed-mode chip, or in a digital ASIC, or by programming a digitalsignal processor (DSP) or a central processing unit (CPU). The best modeof implementation is most likely one where the control signal to changebetween the modes comes from the digital ASIC, DSP or CPU, and locallogic on an analog or a mixed-mode chip steers the transitions betweenmodes. The RF monitoring circuit 10 is preferably implemented on thesame chip with the other RF parts in the receiver. The algorithm used inthis invention may be implemented by calculating the values for receiverparameters in real-time or approximate real-time during reception, or bycalculating the values in advance for different combinations of signalconditions, and then placing the calculated values in a lookup table, orby any other means that can provide the required logic for thealgorithm's execution.

[0143] Of course, for a certain embodiment only a sub-set of theforegoing algorithm and circuitry maybe implemented, and thus the formof the actual deployed embodiment can be a function of the receiversystem type and architecture and the required accuracy, among otherfactors.

[0144] The method and apparatus disclosed herein provides a powerfulreal time or substantially real time adaptive function, and can operatecontinuously or discontinuously. The method and apparatus is alsocapable of optimizing power consumption based on more than simply thereceived signal strength, and can also provide and operate oninformation concerning large interferers. The method and apparatus isalso capable of separating input signals causing interference in theband of interest due to intermodulation from other blocking signals. Atleast theoretically, there is a large difference between blocking andintermodulation as sources of interference from the power scalingperspective. If the logic is based only on blocking, a significantlyhigher power consumption, on the average, is needed as compared to acase where intermodulation and blocking can be separated from oneanother. The background for this difference between the two methods isshown in FIG. 2.

[0145] The method and apparatus in accordance with this invention alsodoes not require a priori knowledge of the interference in order to beeffective, such as knowledge of TX leakage in the RX chain. However, ifthis information is available it can also be used by the algorithm.Significantly, the receiver need not be designed so as to operate at alltimes for the worst-case conditions with respect to the received radiospectrum.

[0146] Unlike some prior art approaches, the method and apparatus inaccordance with this invention are also suitable for use with thosereceivers having continuous reception, such as DS-CDMA with FDD, and donot require that the receiver be tuned to all possible interferingsignal frequencies to be able to scan all possible interferers,otherwise only a selected number of interferers can be estimated. Also,there is no restriction that the interferers cannot be measured duringthe normal signal reception, which limits the accuracy of someconventional methods.

[0147] As was stated above, in CDMA systems where the capacity islimited by noise and interference, and also by other transmittedchannels in the RF band of interest, the use of this invention can bemade to trade-off between noise, interference and other code channels toachieve the required performance. However, this technique requires oneto take some precautions to avoid the disturbance in the power controlloop. A solution to this problem has been presented in copending U.S.patent application Ser. No. 10/034,837, filed on even date herewith, byAarno Päirssinen, Jussi Vepsäläinen and Pauli Seppinen “Method andApparatus for Reducing Power Consumption in Transceivers in WirelessCommunications Systems Having a Power Control Loop” (incorporated byreference herein in its entirety).

[0148] Briefly, and referring to FIG. 15A, a flow chart is shownbeginning with a first step 41 in which the RF receiver system of atransceiver is initialized. The transceiver is assumed to becommunicating with another, second transceiver during the use of thismethod. In a next step 42, power control measurements are performed withthe receiver in a predetermined measurement mode. In a next step 43,power control commands are then sent by the transceiver having thereceiver to the communicating transceiver. Then, if the receiver systemis programmed in accordance with the invention disclosed in theabove-captioned U.S. patent application Ser. No. 10/034,837, filed oneven date herewith, “Method and Apparatus for Reducing Power Consumptionin Transceivers in Wireless Communications Systems Having a PowerControl Loop”, the receiver system waits until no measurements arescheduled and so decides when to enter a tuning mode per a decision step44 a. In a next step 44 b the receiver tuning is enabled; in a next step45, a cycle of adaptive tuning is performed (with a receiver tuninglogic module sending tuning commands to the radio receiver), and at theend of that cycle, if it is time to again measure for power control, ina next step 46, receiver tuning is disabled, and in a next step 47, thereceiver system reconfigures itself for making power controlmeasurements and then returns to step 42 in which it makes the powercontrol measurements. If it is not yet time to measure for powercontrol, the step 45 of performing a cycle of adaptive tuning isrepeated.

[0149] Referring also to FIG. 15B, as seen from another perspective thereceiver system transitions between two different modes 51 and 52. Thesemodes are a receiver tuning mode 51, and a power control measuring mode52. With the receiver initially in the power control measuring mode 52,the receiver transitions to the receiver tuning mode 51 when thereceiver system completes a set of power control measurements. In thereceiver tuning mode, the receiver is adjusted (tuned) to one or anotheradaptively selected internal state. The receiver remains in the receivertuning mode 51 until it is time to make the next set of power controlmeasurements.

[0150] The method and apparatus in accordance with this invention alsoprovides a wider operational range, as switching is not limited when thesignal levels are very weak so as not to significantly disturb thereception. Also, the accuracy of the measurement is more precise as theintermodulation products can be separated from the noise and receivedsignal. The method and apparatus can be configured so as to perform thenecessary gain control function in the receiver, or it can be combinedwith an existing receiver gain control function.

[0151] These teachings also provide a technique to combine the noise andthe linearity performance into the same algorithm, and are therebycapable of reducing the required amount of headroom in the receivercircuit design and implementation.

[0152] Furthermore, these teachings provide the possibility to accepthigher levels for the intermodulation (two-tone) test and the blockingtest in a radio system, since adaptive logic is made available that isscalable according to the intermodulation and blocking. Additionalflexibility in the network design is thus made possible, while stillenabling the average power consumption in the mobile station to beacceptable.

[0153] Thus, while described above in the context of presently preferredembodiments, those skilled in the art should appreciate that theteachings of this invention should not be construed as being limited toonly the above-described presently preferred embodiments.

What is claimed is:
 1. A method for operating a radio frequency RFreceiver, comprising: during operation of the RF receiver, periodicallydetermining existing RF receiver operational conditions; determining RFreceiver performance requirements based at least in part on thedetermined existing RF receiver operational conditions; and allocatingpower consumption between RF receiver functional blocks in accordancewith the determined RF receiver performance requirements and inaccordance with a behavior model of at least one of the RF receiver as awhole and individual functional blocks of the RF receiver.
 2. A methodas in claim 1, where determining existing RF receiver operationalconditions comprises monitoring interfering signals and determiningreceived signal distortion due to at least one of intermodulation andblocking.
 3. A method as in claim 1, where determining existing RFreceiver operational conditions comprises measuring at least one of thereceived signal and internal conditions of a transceiver of which the RFreceiver is apart.
 4. A method as in claim 1, further comprisingmonitoring resulting RF receiver signal quality to determine ifallocating power consumption performed an optimum allocation of thepower consumption.
 5. A method as in claim 2, where monitoringinterfering signals monitors the signals in at least one of the RF, IFand BB sections of the receiver.
 6. A method as in claim 3, wheremeasuring the received signal measures the received signal at BB.
 7. Amethod as in claim 6, where measuring the received signal at BB resultsin a measurement of at least one of RSS, SIR, Ec/Io, BER and BLER.
 8. Amethod as in claim 1, where determining RF receiver performancerequirements determines at least the gain of the RF receiver.
 9. Amethod as in claim 1, where determining RF receiver performancerequirements determines at least the noise factor of the RF receiver.10. A method as in claim 1, where determining the RF receiverperformance requirements determines at least the third-order inputintercept point of the RF receiver.
 11. A method as in claim 1, wheredetermining the RF receiver performance requirements determines at leastthe second-order input intercept point of the RF receiver.
 12. A methodas in claim 1, where determining the RF receiver performancerequirements determines at least the input compression point of the RFreceiver.
 13. A method as in claim 1, where determining the RF receiverperformance requirements determines at least the phase noise of the RFreceiver.
 14. A method as in claim 1, where determining the RF receiverperformance requirements also determines a correct value of gain for theRF receiver.
 15. A method as in claim 1, where allocating powerconsumption between RF receiver functional blocks operates by at leastone of: varying at least one of the biasing current and the power supplyvoltage, by bypassing at least one stage, by switching between stages,and by changing feedback.
 16. A communications device comprising a radiofrequency RF receiver, further comprising monitoring circuitry, operableduring operation of the RF receiver, for periodically determiningexisting RF receiver operational conditions and for determining RFreceiver performance requirements based at least in part on thedetermined existing RF receiver operational conditions, saidcommunications device further comprising power control circuitry forallocating power consumption between RF receiver functional blocks inaccordance with the determined RF receiver performance requirements andin accordance with a behavior model of at least one of the RF receiveras a whole and individual functional blocks of the RF receiver.
 17. Acommunications device as in claim 16, where said monitoring circuitrymeasures interfering signals and determines received signal distortiondue to at least one of intermodulation and blocking.
 18. Acommunications device as in claim 16, where said monitoring circuitrymeasures at least one of the received signal and internal conditions ofa transceiver of which the RF receiver is apart.
 19. A communicationsdevice as in claim 16, where said power control circuitry is responsiveto resulting RF receiver signal quality for determining if the allocatedpower consumption is an optimum allocation of the power consumption. 20.A communications device as in claim 16, where said monitoring circuitrymonitors a received signal in at least one of the RF, IF and BB sectionsof said RF receiver, and where monitoring the received signal at BBcomprises a measurement of at least one of RSS, SIR, Ec/Io, BER andBLER.
 21. A communications device as in claim 16, where said monitoringcircuitry operates to determine at least one of: the gain of the RFreceiver, a correct value of the gain of the RF receiver, the noisefactor of the RF receiver, the third-order input intercept point of theRF receiver, the second-order input intercept point of the RF receiver,the input compression point of the RF receiver, and the phase noise ofthe RF receiver.
 22. A communications device as in claim 16, where saidpower control circuitry operates by at least one of: varying at leastone of the biasing current and the power supply voltage, by bypassing atleast one stage, by switching between stages, and by changing feedback.